On Mon, Dec 3, 2018 at 9:42 PM Feng Tang <feng.t...@intel.com> wrote:
>
> When kernel panic happens, it will first print the panic call stack,
> then the ending msg like:
>
> [ 35.743249] ---[ end Kernel panic - not syncing: Fatal exception
> [ 35.749975] ------------[ cut here ]------------
>
> The above message are very useful for debugging.
>
> But if system is configured to not reboot on panic, say the "panic_timeout"
> parameter equals 0, it will likely print out many noisy message like
> WARN() call stack for each and every CPU except the panic one, messages
> like below:
>
> WARNING: CPU: 1 PID: 280 at kernel/sched/core.c:1198
> set_task_cpu+0x183/0x190
> Call Trace:
> <IRQ>
> try_to_wake_up
> default_wake_function
> autoremove_wake_function
> __wake_up_common
> __wake_up_common_lock
> __wake_up
> wake_up_klogd_work_func
> irq_work_run_list
> irq_work_tick
> update_process_times
> tick_sched_timer
> __hrtimer_run_queues
> hrtimer_interrupt
> smp_apic_timer_interrupt
> apic_timer_interrupt
>
> For people working in console mode, the screen will first show the panic
> call stack, but immediately overridded by these noisy extra messages, which
> makes debugging much more difficult, as the original context gets lost on
> screen.
>
> Also these noisy messages will confuse some users, as I have seen many bug
> reporters posted the noisy message into bugzilla, instead of the real panic
> call stack and context.
>
> Removing the "local_irq_enable" will avoid the noisy message.
>
> The justification for the removing is: when code runs to this point, it
> means user has chosed to not reboot, or do any special handling by using
> the panic notifier method, no much point in re-enabling the interrupt.
>
> Signed-off-by: Feng Tang <feng.t...@intel.com>
> Cc: Thomas Gleixner <t...@linutronix.de>
> Cc: Kees Cook <keesc...@chromium.org>
> Cc: Borislav Petkov <b...@suse.de>
> Cc: sta...@kernel.org
Acked-by: Kees Cook <keesc...@chromium.org>
-Kees
> ---
> kernel/panic.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/kernel/panic.c b/kernel/panic.c
> index f6d549a..a616e55 100644
> --- a/kernel/panic.c
> +++ b/kernel/panic.c
> @@ -295,7 +295,6 @@ void panic(const char *fmt, ...)
> }
> #endif
> pr_emerg("---[ end Kernel panic - not syncing: %s ]---\n", buf);
> - local_irq_enable();
> for (i = 0; ; i += PANIC_TIMER_STEP) {
> touch_softlockup_watchdog();
> if (i >= i_next) {
> --
> 2.7.4
>
--
Kees Cook
